Combination telephone and intercommunications system



R. TRUBY Feb. 14, 1967 COMBINATION TELEPHONE AND INTERCOMMUNICATIONS SYSTEM Filed Jan 30, 1964 8 Sheets-Sheet 1 UUR cose@ C@ .Wl Q WHW REN vm /Nl/ENTOR R. maar @CLJ/b A TTORNEV R. TRUBY Feb. 14, 1967 COMBINATION TELEPHONE AND INTERCOMMUNICATIONS SYSTEM Filed Jan. 50, 1964 8 Sheets-Sheet 2 R. TRUBY Feb. 14, 1967 COMBINATION TELEPHONE AND INTERCOMMUNICATIONS SYSTEM 8 Sheets-Sheet 5 Filed Jan. 30, 1964 R. TRUBY Feb. 14, 1967 COMBINATION TELEPHONE AND INTERCOMMUNICATIONS SYSTEM Filed Jan. 30, 1964 8 Sheets-Sheet 4 R. TRUBY 3,304,376

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R. TRUBY Feb. 14, 1967 COMBINATION TELEPHONE AND INTERCOMMUNICATIONS SYSTEM Filed Jan. 30, 1964 8 Sheets-Sheet 7 R. TRUBY Feb. 14, 1967 8 Sheets-Sheet 8 MIDE@ United States Patent O 3,304,376 COMBINATION TELEPHONE AND INTER- COMMUNICATIONS SYSTEM Ralph Truby, Rumson, NJ., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Jan. 30, 1964, Ser. No. 341,176 23 Claims. (Cl. 179-42) My invention relates generally to telephone systems, more particularly to integrated telephone and intercommunciation systems, and specifically to telephone systems wherein local stations of an intercommunication network communicate with each other by way of individual local intercommunication channels and communicate with stations outside the intercommunication network by way of individual telephone channels connected to a telephone exchange.

Many business establishments, particularly hospitals, re-

quire communication facilities permitting intercommunication within a relatively small group of local stations as well as -communication facilities permitting communication between stations of the local group and other local and nonlocal stations outside the local group. For example, hospitals generally require four basic types of communication facilities: first, facilities are provided allowing administrative and staff personnel to communicate locally among themselves and with others not physically within the hopsital; second, facilities are provided for nurses to select, signal and communicate with each patient in their charge; third, facilities are provided allowing patients to communicate locally with each other and nonlocally with others outside the hospital; and fourth, facilities are provided whereby patients can alert their nurse to their need for assistance or other attention. The above communication requirements are usually fullled by three separate and distinct systems. A telephone exchange or PBX is provided to permit hospital administrators, staff and patients to communicate among themselves and with the outside world. A patient controlled nurse-call arrangement, which includes facilities for generating appropriate audible and visual signals, is provided to permit patients to alert their nurse. A nurse controlled, two-way, communication system is provided to permit a nurse selectively lto signal and communicate with each patient in her charge. The installation and maintenance of three separate communication systems on a single premises to perform the above communication functions is costly and inefficient. Duplication of equipment components having similar functions in the separate systems unnecessarily increases the cost of installation `as well as the -cost of maintaining the separate systems. Also, little flexibility exists in the manner in which the separate systems may be cooperatively used.

Accordingly, an object of my invention is to decrease the cost of maintaining and installing communication facilities which fulfill the communications requirements of business establishments in general and of hospitals in particular.

Another object of my invention is -to increase the cooperative eiciency and exi'bility of communications facilities which fulfill the communications requirements of business establishments in general and of hospitals in particular.

Prior art local intercommunication arrangements are of two general types. As utilized in hospitals for nursepatient communication, these arrangements generally comprise either a two-way loudspeaker system or a key telephone system. The loudspeaker type system permits a nurse to select a patient station, to signal the selected station and to converse with the patient over a loudspeaker loacted in the patients room. This type of arrangement ice is adavntageous in that no manual act by the patient is necessary for the patient to -converse with the nurse, i.e., hands-free patient operation is provided. However, in the loudspeaker type arrangement, a nurse-patient conversation is not private as it is broadcast over the loudspeaker so that all in the patients room can hear. A key telephone system Ipermits a nurse to select and signal a patient station and to converse with the patient after the handset of the patient station has been lifted and placed in a position suitable for the patients use. The key telephone arrangement aifords the conversational privacy which was lacking in the loudspeaker type system, but it does not have the hands-free patient operation advantage of the loudspeaker arrangement. If a patient is physically incapacitated or is otherwise occupied, it may be physically impossible or highly inconvenient for him to perform the manual act of lifting his handset to answer the nurses signal.

Accordingly a further object of my invention is to permit the selective use of local intercommunication facilities on either a hands-free basis or a manual -basis in accordance with the immediate physical capacity and privacy requirements of each individual station user.

The above and other objects of my invention are attained in one illustrative embodiment thereof which is described herein, by way of example, in terms of its use in a hospital. Each patient station terminates an individual intercommunication channel in a microphone and loudspeaker arrangement incorporated in the patient station. Each patient station also terminates a telephone channel associated with the telephone handset of the patient station. The respective patient telephone channels are normally connected to a telephone exchange and are used for regular telephone calls to and from the respective patients. Each patient station is equipped with a signaling key or keys which, when actuated lby a patient, initiate the generation of appropriate audible `and visual nurse-call signals to alert the nurse.

Each nurse station is intercommunicatively associated with one group of patient stations comprising the stations of patients in the nurses charge. A nurse station is equipped with an intercommunication channel and with one or more telephone channels. The telephone channels are connected directly to the telephone exchange and are used for regular telephone calls to and from the nurse station. f

The nurse station is further equipped with a discrete patient station selection key for each patient station in the intercommunication network. By operating a station selection key, the nurse effects the establishment of a connection between the nurse station intercommunication channel and the intercommunication channel of the patient station defined by the operated station selection key. The nurse can then converse through her handset or speakerphoneI with the selected patient via the connected intercommunication channels and the loudspeakermicrophone arrangement at the selected patient station. No physical act is required of the patient at the selected patient station to answer the nurses call, and hands-free patient operation is thus provided.

In accordance with an aspect of my invention, the patient can, at his discretion, initiate a transfer of the nursepatient conversation from his intercommunication channel to his telephone channel, thereby permitting a more private nurse-patient conversation. The transfer is initiated merely by lifting the patient station handset and thus operating the switchhook contact of the patient station. When a patient and his nurse are conversing over their connected intercommunication channels, the operation of the patient station switchhook contact automatically initiates the disconnection of the patient station telephone channel from the telephone exchange, the disconnection of .the patient station intercommunication channel from the nurse station intercommunication channel and the connection of the patient station telephone channel to the nurse station intercommunication channel. Thus each patient, at his own discretion, can select either his relatively public, hands-free, intercommunication chan- -nel or his relatively private, telephone channel for conversing with the nurse.

A nurse station is equipped with means for transferring audible nurse-call signals to a remote location. Means are provided whereby a station located at the remote location may be automatically connected to the inf tercommunication channel of a calling patient station when the handset of the remote station is lifted. Thus,

when a nurse station is left unattended, calls from the various patients to their nurse can be answered at the remote station.

In accordance with a feature of my invention, communications facilities which fulll both internal and external signaling and communication requirements of business establishments in general and of hospitals in particular are incorporated into a single communication system.

In accordance with another feature of my invention,

stations within an intercommunication network comprise -apparatus permitting selective intercommunication either hands-free or under manual control at the discretion of each station user.

In accordance with a more specific feature of my invention, stations within an intercommunication network are individually equipped to manually control a corresponding telephone channel normally connected to a telephone exchange and to permit hands-free intercommunication via another channel connected to the intercommunication network; the manually controlled telephone 4channel being automatically transferrable from the telephone exchange to the intercommunication network -responsive to operation of the switchhook contact of the station.

The above and other objects and features of my invention will be more fully understood from the following description when read with reference to the drawing wherein: Y

FIG. 1 shows, in block diagram form, a communication system illustrative of my invention as it may be installed in a hospital;

FIG, 2 shows a nurse station, a remote station and a telephone exchange; the nurse station being illustrated schematically, and the remote station and telephone exchange being represented in block diagram form;

FIGS. 3 and 6 show, in schematic form, the patient stations of the system;

FIGS. 4, 7 and 8 respectively show, in schematic form, the patient station control circuits associated with the patient stations of FIGS. 3 and 6;

FIG. shows, in schematic form, the nurse station control circuit and other common intercommunication control equipment; and

FIG. 9 indicates the manner in which FIGS. 2-8 are arranged.

The detached contact method of illustration has been adopted in the drawing. In this method, a relay winding is shown physically separated from the relay contacts controlled thereby. This permits placement of the relay contacts at locations in the circuit drawing at which the functions performed thereby are visually pertinent, and avoids the necessity of employing a large number of unnecessarily long connecting lines. In this method of illustration, break contacts, i.e. those contacts of a relay which are closed when the relay is released and open when the relay is operated, are illustrated by a short line perpendicular to the conductor to which they are connected, for example break contact 5X-1 on FIG. 5. Make contacts, i.e. those contacts of a relay which are open when the relay is released and closed when the relay is operated, are illustrated by a pair of diagonal lines forming an X which intersect the conductor to which they are connected, for example make contact 5S-4 on FIG. 5.

Relay contacts are identified by a designation corresponding to that of the relay winding by which they are controlled. For example, make contact SN-l connected to lead 519 and make contact 5N1-3 connected to lead 204 on FIG. 5 are controlled by the correspondingly designated relay SNI. on FIG. 5. In addition to the relay designation, the contacts controlled thereby are numerically designated with an additional digit. For example, make contact SNI-1 is one relay contact controlled by relay SNI and make contact 5N 1 3 is another relay contact controlled by relay 5N1. Where a make and a break Contact are identically designated, for example make and break contacts SWT-1 on FIG. S, they represent transfer contacts.

Relays, leads, cables and other circuit elements are designated so as to indicate the number `of the drawing gure on which they appear or from which they originate. For example, the initial digit 5 of the relay designation 5N1 indicates that relay 5N1 and the relay contacts thereof are shown in FIG. 5. Similarly, the initial digit 5 of the lead designation 503 indicates that lead 503 may be considered as originating on FIG. 5. Where possible, circuit elements and equipment items have been given functional designations, and the designation of corresponding circuit elements is consistent throughout the drawing to facilitate interpretation of the drawing.

GENERAL DESCRIPTION System arrangement (FIG. 1)

FIG. 1 illustrates one manner in which my invention may be installed for use in a hospital. A nurse station NSl is intercommunicatively associated with a plurality of patient stations PS1-P860, of which patient stations PS1, P530 and P860 are shown, to form an intercommunication network. Common equipment 103 is provided to perform the necessary switching operations for selectively connecting nurse station NS1 with patient stations PS1-PS60. Remote station RSI is provided for answering patient-to-nurse calls when nurse staion NSl is unattended. All of the stations NSI and PS1-PS60 are given access to telephone exchange 104, whereby outside calls may be made to and from other telephone stations inside or outside the hospital.

Telephone exchange 104 may comprise any well-known type of manual or automatic telephone switching center. It provides facilities for selectively interconnecting the various hospital stations connected thereto and for selectively connecting hospital stations with outside stations and with trunk circutis to distant telephone exchanges. If a sufficient number of hospital stations are required, telephone exchange 104 may be a PBX physically located within the hospital plant or, if a relatively small number of hospital stations are required, telephone exchange 104 may be a telephone central office located outside the hospital plant which serves other telephone stations in addition to the hospital stations.

Among the various hospital stations connected to telephone exchange 104 are nurse stations, such as NSI, patient stations, such as PS1, PS30 and P860, and other stations (not shown) used by hospital administrative and staff personnel. Where hospital stations are equipped with more than one telephone channel, telephone exchange 104 may include the key telephone control equipment necessary for the selective use of multiple lines by -a single station. Since such telephone exchanges and the components thereof are well known in the telephone art and since further details thereof are not necessary for an understanding of my invention, no detailed description of telephone exchange 104 is included herein. Y Each patient station PS1-PS6!) is connected to commonI equipment. 103, through a control cable PCC1.-

PCC60. The control cables PCCI-PCC60 include various leads over which control signals are transmitted between the respective patient staions PSI-P860 and common equipment 103. A similar control cable NCC connects nurse station NSI with common equipment 103.

Each patient station PSI-P560 is connected to common equipment 103 by a patient intercommunication channel PIC1-PIC60. Nurse station NSI is connected to common equipment 103 by a nurse intercommunication channel NIC. In response to station selection signals generated at nurse station NSI, common equipment 103 effects connections between nurse intercommunication channel NIC and a selected patient intercommunication channel PIC1-PIC60.

Remote intercommunication channel RIC connects remote station RSI to common equipment 103 to facilitate answering of patient-to-nurse calls at remote station RSI. Common equipment 103 automatically connects remote intercommunication channel RIC to the patient intercommunication channel PIC1-PIC60 of a calling patient station PS1-P860.

Each patient station PS1-P560 is connected through common equipment 103 to telephone exchange 104 by a patient telephone channel PTC1-PTC60. Patient telephone channels PTC1-PTC60 are used for outside telephone calls to and from patient stations PSI-P860. Means are provided in common equipment 103 to transfer patientnurse conversations from a patient intercommunication channel PIC1PIC60 to the corresponding patient telephone channel PTCI-PTC60 and to disconnect telephone exchange 104 from the appropriate patient telephone channel PTC1-PTC60.

Nurse station NSI is connected to telephone exchange 104 by one or more nurse telephone channels NTC. Calls to and from stations outside the intercommunication network are originated or answered at nurse station NSI by way of the nurse telephone channels NTC and telephone exchange 104.

System equipment (FIGS. 2 8) PATIENT STATIONS PSI-PSGO (FIGS. 3 AND 6) Patient stations, such as PS1, may be provided on an individual patient basis or may be shared by a plurality of patients in the same room. The patient in private room 100 signals his nurse by operating his nurse-call key NCK1 or by operating a pendant button (not shown) on -a cord for which pendant cord jacks PJAI and PJBI are provided at patient station PS1. The momentary operation of either the nurse-call key NCK1 or the pendant button (not shown) signals common equipment 103 to initiate a plurality of 60 i.p.m. nurse-call signals, both audible and visual. These 60 i.p.m. nurse-call signals indicate that a particular patient requests attention. Among the visual nurse-call signals are a flashing door lamp DLI located outside the door of the calling patients room 100, a flashing patient lamp PLI incorporated in the individual patient station PS1 and a flashing station lamp SL1 located at the nurse .station NSI of FIG. 2. Nurse-call signals originated from patient stations in a multipatients ward 102, such as stations P830 and P860, are indicated by the single door lamp DL30 outside the door of the ward 102 in which the calling patient is located. Audible nurse-call signals are indicated by a buzzer NBI at the nurse station NSI of FIG. 2.

The patient at station PS1 may cancel his request for assistance and retire the 60 i.p.m. audible and visual nurse-call signals by operating the nurse-call release key NCRKI on his station PSI.

When a nurse answers the patients nurse-call signal at the nurse station NSI, a short burst of audible tone is heard over speaker SI at patient station PS1. This tone indicates to the patient that the nurse is connected to his intercommunication channel PICI and that she can hear any conversation in his room by way -of microphone M1. Following the short burst of audible tone, the nurse and patient may converse over microphone M1 and speaker S1 incorporated in patient station PS1. If the patient desires a more private conversation with his nurse, he merely lifts the telephone handset PHSI of his station PSI. The nurse-patient conversation is then automatically transferred from the microphone M1 and speaker SI to the patient station handset PHSI.

The patient station handset PHSI is also used by they patient to originate and answer regular telephone calls by way of telephone exchange 104. Each patient station, such as PS1, is equipped with a ringer PRI which generates audible signals in response to ringing current transmitted from telephone exchange 104 to indicate an incoming call. Handset PHSI is similar to that described in C. F. Mattke Patent 3,073,911, issued January 15, 1963. It includes a dial for generating call information signals to which telephone exchange 104 responds. The telephone handset PHSI and the microphone M1 and speaker SI may be used concurrently for a regular telephone call and for a nurse-patient conversation. However, should the patient desire a private conversation with his nurse, he must terminate the regular telephone call before the nurse-patient conversation can be transferred to the telephone handset PHSI.

If a patient desires complete privacy, he may operate the privacy key PKI on his station PS1. In an operated condition, key PKI opens the circuit of microphone MI so that the nurse cannot eavesdrop -on conversations in the patients room. Operation of key PKl also applies an audible tone to the circuit of microphone MI. This tone alerts the nurse that the patient does not wish to be disturbed. However, the patient cannot disable his speaker SI, and the nurse can talk to him at any time.

An emergency key EKI is provided at a strategic location or locations associated with the individual patient. Operation of emergency key EKI causes common equipemnt 103 to initiate various audible and visual emergecy signals different from the normal nurse-call signals. The emergency signals initiated as a result of an operated emergency key EKI cannot be retired unless emergency key EKI is manually released. This necessitates the physical presence of the nurse at the location of emergency key EKI or the release of emergency key EKI by the patient.

Each patient station, such as PSI, is equipped with a data jack DJI. Data jack DJI provides access to telephone exchange 104 over telephone channel PTCI whereby diagnostic data, such as electrocardiogram signals, may be transmitted to a selected location within the hos-l pital for analysis.

Each patient station, such as PS1, is equipped with a `call-waiting lamp CWLI whereby the patient may be notified that an incoming telephone call from telephone exchange 104 is awaiting his answer. Lamp CWLI may be advantageously used when telephone exchange 104 is manually controlled. It is lighted under the control of an operator at the switchboard of telephone exchange 104 to indicate an unanswered waiting call or a message to be delivered to the patient.

.NURSE VSTATION lNSl (FIG. 2)

Nurse stations, such as NSI, are provided at central locations throughout the hospital which are physically near the patients under the charge of the respective nurses. In the illustrative system described herein, nurse station NSI is equipped for intercommunicative association with a network comprising a maximum of sixty patient stations PS1-PS60. However, the number of patient stations associated with a nurse station is exible and may be easily varied by simple equipment additions.

A nurse station NSI is equipped with one or more telephone channels, such as NTCI, which are directly connected to telephone exchange 104. If more than one telephone channel NTCI is provided, telephone exchange 104 may include key telephone equipment permitting ilexible, selective use of the various telephone channels, as is well known in the art. Telephone channels, such as NTCI, are selected for use by the nurse by operating an appropriate line pick-up key, such as LPKI, on her station NSI.

A nurse calls a selected patient station, for example PS1, by operating the intercommunication pick-up key IPKI, lifting the nurse station handset NHSI and then operating the station selection key SSKI discretely delining the selected patient station PS1. When key IPKI is operated and handset NHSI is raised, a tone is transmitted to the nurses handset NHSI indicating to the nurse that the nurse station NSI is connected to the intercommunication network. When station selection key SSKI is subsequently operated, the tone is momentarily transmitted to the selected patient station PSI, indicating to the patient that the nurse is conneced to his intercommunication channel PICI. The tone is then cut off from the nurses handset NHSI and the patient station PSI, and the nurse can converse with the selected patient through the nurse station handset NHSI. If desired, nurse station NSI may be equipped with a speakerphone arrangement (not shown) similar to that described in W. F. Clemency Patent 3,075,045, issued January 22, 1963, to provide the nurse with hands-free operation.

Each stati-on selection key SSK1-SSK60 has a discrete station lamp SLI-SL60 associated therewith which flashes at 60 i.p.m. when the patient at the station PS1 dened by the station selection key SSKI, has operated his nurse call key NCKI. To answer a patient-to-nurse-call signal, the nurse operates the station selection key SSKI- SSK60 associated with the flashing lamp SLI-SL60. The lamp SLI-SL60 then ceases to flash and remains continuously lighted until the nurse releases the nurse-patient connection. A nurse-patient connection can be released either by replacing handset NHSI, by releasing key IPKI or by depressing another station selection key SSKI- SSK60.

Nurse station NSI is equipped with a ringer NRI to indicate incoming telephone calls from telephone exchange 104 and a buzzer NBI to indicate calls from patient stations PSI-PS60. Emergency signals from patient stations PSI-PS60 are indicated at nurse station NSI when the station lamp SLI-SL60 defining the calling patient station PSI-PS6() flashes at 120 i.p.m. and buzzer NBI is continuously sounded.

Nurse station NSI is further equipped with a remote station transfer key RTKI. When key RTKI is operated, nurse-call and emergency audible signals from patient stations PSI-PS60 are transmitted to another station RSI remote from nurse station NSI.

REMOTE STATION RSI (FIG. 2)

Since it is possible that nurse station NSI may be unattended at times, a remote station RSI is provided from which patient-to-nurse calls can be answered. Remote station RSI may be located centrally with other remote stations associated with different nurse stations, or it may be at some normally attended location in the immediate vicinity of the patients in the charge of the nurse at nurses station NSI.

When transfer key RTKI at nurses station NSI is operated, patient-to-nurse-call signals are transmitted to remote station RSI, A patient-to-nurse call is answered at remote station RSI merely by lifting the handset RHSI. Common equipment 103 then automatically connects remote station RSI to the calling patient station PSI-P860. If more than one patient station PSI-P860 is calling the nurse, the connection is made through a preference lockout circuit in common equipment 103 which permits connection of remote station RSI to only one patient station PS1-P860 at a time.

Common equipment 103 (FIGS. 4, 5, 7 and 8) Each patient station PSI-P860 is connected to an individual patient station control circuit in common equipment 103. FIG. 4 schematically illustrates the patient station control circuit for patient station PS1 of FIG. 3. FIGS. 7 and 8 respectively illustrate the patient station control circuits for patient stations P530 and P860 of FIG. 6. A patient station control circuit, for example FIG. 4, provides controllable switching whereby nursepatient conversations may be transferred from a patient station microphone MI and speaker SI to the patient station handset PHSI. A patient station control circuit also includes circuitry which responds to patient-to-nursecall signals and emergency signals from the associated patient station PSI to initiate the appropriate audible and visual signals for alerting the nurse.

FIG. 5 schematically illustrates the control circuitry for nurse station NSI and other equipment common to the intercommunication network. A central voice-switching control unit SVSCU is included in the common equipment 103. Control unit SVSCU facilitates connection of the bidirectional nurse intercommunication channel NIC to the unidirectional microphone MI and the unidirectional speaker SI of a selected patient station PSI, Copending patent application of lV. F. Clemency et al., Serial No. 60,476, tiled October 4, 1960, describes such a voice-switching circuit. Sincet he detailed operation of control unit SVSCU is not necessary for an understanding of my invention, no detailed description thereof is included herein.

Common equipment 103 also includes a tone source STS. Tone source STS generates the aforenoted audible signal which is transmitted to the nurse station handset NHSI and to a patient station speaker SI when patient station PSI is selected by the nurse at nurse station NSI. Since such tone sources are well known in the art and details thereof are not necessary for an understanding of my invention, no further description of tone source STS is included herein.

Interrupter circuit 530 of common equipment I03 transmits the various control potentials interrupted at appropriate intervals to control the audible and visual signaling devices indicating nurse-call and emergency signals from a patient. Interruptor circuits providing interrupted control potentials are well known in the telephone art and the details thereof are not necessary to an understanding of my invention. No detailed description of interrupter 530 is included hereinbelow.

Common equipment 103 also includes a power supply (not shown) which supplies the potentials for the intercommunication network. The potentials supplied by the power supply include negative potential and ground potential for controlling the operation of the relays and transistors o f the station control circuits, alternating potential LB for lighting the various lamps at nurse station NSI and patient stations PSI-P860 and alternating potential BB for activating buzzer NBI at nurse station NSI and buzzer RBI at remote station RSI. Power supplies of the type required to supply the aforenoted potentials are well known in the art and no description thereof is given herein.

DETAILED DESCRIPTION Patient-tomarse call PATIENT-TO-'NURSE lCALL iSIGNALING Each patient station, for example patient station PSI on FIG. 3, is equipped with a nurse-call key NCKI which the patient operates to call his nurse. Each patient station is further equipped with jacks such as PJAI and PJBI into which pendant button cords (not shown) may be inserted for use by patients who are physically unable to reach the nurse-call key NCKI. When key NCKI or a pendant button is momentarily operated by the patient, various audible and visual nurse-call signals are initiated to alert the nurse.

'The operation of key NCK1 or of a pendant button (not shown) applies ground potential through the operated key NCK1 or button to lead 309. The emitter of transistor 4T3 on FIG. 4 is connected to lead 309. The base of transistor 4T3 is connected through resistor 4R6 to negative potential. Thus, the application of ground potential to lead 309 forward biases the emitter-base junction of transistor 4T3 causing transistor 4T3 to be turned ON.

When transistor 4T3 is turned ON, a circuit for operating relay 4NC is completed. This operating circuit extends from negative potential through the winding of relay 4NC and transistor 4T3 to the ground potential on lead 309. Relay 4NC is operated over this circuit, and locks operated over a circuit extending from negative potential through its winding, transistor 4T3, varistor 4V2, and make contact 4NC-2, over lead 409 and through break contacts 4P1-1 and 4P2-1 to ground potential.

The operation of relay 4NC completes an operating circuit for start relay SST. Relay 5ST operates over a circuit extending from negative potential through its winding, over lead S02, through diode 4D6 and make contact 4NC-2, over lead 409, and through break contacts 4PI-I and 4P2I to ground potential. The operation of relay 5ST completes ia circuit for activating interrupter 530, Which extends from alternating potential LB through make contact SST-4 and over start lead 520 to interrupter S30.

The respective outputs of interrupter 530 as indicated on FIG. 5 are applied to leads S03, S06, S07, 50S and 509. The outputs consist of ground potential, alternating potential LB and alternating potential BB each interrupted either sixty or one hundred twenty times each minute.

Lead S08 has ground potential applied thereto interrupted sixty times per minute (60 i.p.m.). This 60 i.p.m. ground potential is applied over lead S08 through resistor 4R1, make contact 4NC-4, and break contact 4E-6 to the base element of transistor 4T4. The emitter of transistor 4T4 is connected through varistor 4V3 to negative potential. Thus, the application of ground potential to the base of transistor 4T4 forward biases the base-emitter junction thereof and causes transistor 4T4 to be turned ON.

When transistor 4T4 is turned ON, a circuit for operating door lamp control relay DLC1 on FIG. 3 is cornpleted. This circuit extends from negative potential through varistor 4V3 and transistor 4T4, over lead 302 and through the winding of relay DLC1 to ground potential. When relay DLC1 is operated, the door lamp DLI of room 100 is lighted over a circuit including make contact DLC1-I. Thus, a transistor 4T4 is turned OFF and ON in response to the 60 i.p.m. ground potential applied to its base, the door lamp DLI flashes at 60 i.p.m. to indicate visually the origination of a patient-to-nurse call.

Lead 506 has alternating potential LB applied thereto interrupted sixty times each minute by interrupter S30.

This 60 i.p.m. 'alternating potential LB is applied over lead 506 through break contact 4E-I, make contact 4NC- 3, and break contact 4PI-2 to leads 411 and 311. Lead 311 is connected to patient lamp PLI at patient station PSI. L'arnp PLI ilashes on and ol sixty times a minute responsive to the application thereto of 60 i.p.m. alternating potential LB. The flashing patient lamp PLI visually indicates to the patient that the nurse has been signaled.

Lead 411 is connected to station lamp SLI at nurse -station NSI shown in FIG. 2. Station lamp SLI is discretely associated with patient station PS1. Lamp SLI ashes on and off responsive to the application thereto of the 60 i.p.m. alternating potential LB over lead 411. The 60 i.p.m. dashing of station lamp SLI visually indicates to the nurse that :the patient at patient station PS1 has initiated a patient-to-nurse call.

Lead S03 has alternating potential BB applied thereto interrupted sixty times each minute by interrupter S30. This 60 i.p.m. alternating potential BB is applied over lead 503 through make contact 4NC-4 to lead 217. Lead 217 is Vconnected to buzzer NB1 at nurse station NSI on FIG. 2. Buzzer NB1 generates a 60 i.p.m. audible signal responsive to the 60 i.p.m. alternating potential BB applied thereto. This 60 i.p.m. signal audibly indicates to the nurse that one of her patients has initiated a patient-tonurse call.

REMOTE ySCLAJEION lSIGNALI'NG The nurse station NSI of FIG. 2 is equipped With a remote station transfer key RTKI which, when operated, connects the remote station RSI to the signaling and talking conductors of the system. Key lRTKI is a locking key, i.e. when operated it remains operated until manually released. If key RTKI is operated, ground potential is supplied to remote buzzer RBI over lead 225, and buzzer RBI provides a 60 i.p.m. audible signal at the remote station RSI. Thus, a signal is provided Iat the remote station RSI similar to that provided at the nurse station NSI to indicate audibly the initiation of a patient-tonurse call.

CANCELLATION OF `CALL BY PATIENT Patient station PSI on FIG. 3 is equipped with a nursecall release key NCRKI. Key NCRKI may be physically located beyond reach of the patient, if desired. Key NCRKI is operated when a patient Wishes to cancel a previously initiated patient-to-nurse call before the call is answered by the nurse. Momentary operation of key NCRKI applies ground potential over lead 310 to the base of transistor 4T3. The application of ground potential to the base of transistor 4T3 rem-oves the forward bias from its emitter-base junction and turns transistor 4T3 OFF. When transistor 4T3 is turned OFF, the locking circuit for relay 4NC is opened and relay 4NC is released. The release of relay 4NC removes the above-described 60 i.p.m. signaling potentials supplied through interrupter 530 from the various lamps PLI, DLI, SLI and buzzers NB1, RBI and releases relay SST to deactivate interrupter 530. Thus, the operation of nurse-call release key NCRKI eiectively cancels the patient-to-nurse call and returns the patient station control circuit of FIG. 4 and the control circuits of FIG. 5 to their respective conditions.

@NURSE A'N'SWER In response to the above-described audible and visual nurse-call signals indicating the initiation of a patient-tonurse call from the patient station PSI, the nurse at nurse station NSI answers the call by lifting the nurse station handset NHSI, operating the intercom pick-up key IPKI and momentarily operating the station selection key SSKI discretely -associated with the flashing station lamp SLI. When the nurse picks up the nurse station handset NHSI, ground potential is applied through the switchhook contact (not shown) of nurse station NSI to lead 224. Intercom pick-up key IPKI is a locking type key which remains operated until manually released. When key IPKI is operated, the ground on lead 224 is applied through key IPKI to lead 203, and over lead 203 through the winding of relay SNI to neg-ative potential. Relay SNI is operated over this circuit.

When relay SNI operates, negative potential is applied through make Contact SNI-I to lead 519, which is connected to the winding of relay SWT and is also Aconnected through resistors 5R6 and SR2 to the base of transistor STI. The emitter of transistor STI is connected through varistor SVI to ground potential. Therefore, the application of negative potential over lead S19 to the base of transistor STI forward biases the emitter-base junction of transistor STI causing transistor ST1 to be turned ON. When transistor STI is turned ON, a circuit is completed for operating relay SWT, extending from the negative l I potential on lead S19 through the Winding of relay SWT, transistor ST1 and varistor SVI to ground potential.

Tone source STS may comprise -any Well-known type of oscillator or signal generator. When relay SWT is not operated, the output of tone source STS is applied over lead S17 and lthroLgh break contact SWT-1 directly to ground potential. When relay SWT is operated, the output of tone source STS is applied through make contact SWT-1 to lead S16, which is connected to the tip conductor 207 of the nurse intercommunication channel NIC.

The aforedescribed operation of intercom pick-up key IPKI connected the handset NHSI of nurse station NS1 over tip and ring leads 222 and 223 through the operated key IPKI to the nurse intercommunication channel NIC comprisingA tip and ring leads 206 and 207. The tone supplied by tone source STS is transmitted over nurse intercommunication channel NIC to the handset NHSI of nurse station NSI. This tone audibly indicates to the nurse that she is connected to the intercommunication system and may proceed to select a patient station for communication therewith.

The operation of relay SNI also completes a circuit for lighting intercom lamp ILI at nurse station NSI. Continuous alternating potential LB is applied through make contact SNI-3 and over lead 204 to intercom lamp ILI. The lighting of intercom lamp ILI visually indicates to the nurse that she is connected to the intercommunication system.

When relay SNI operates, an operating circuit for relay SN2 is completed. Negative potential is applied through make contact SNI-I, resistor SR1 and diode SDI to the base of transistor ST2. Ground potential is applied through varistor SV2 to the emitter of transistor ST2. The emitter-base junction of transistor ST2 is thus forward biased, and transistor ST2 is turned ON. When transistor ST2 turns ON, relay SN2 operates over .a circuit extending from negative potential through make contact SNI-1, the Winding of relay SN2, transistor ST2 and Varistor SV2 to ground potential.

The nurse now selects the calling patient station PS1 by momentarily operating the station selection key SSKI discretely associated with the flashing station lamp SLI. When key SSKI is operated, ground potential is applied to lead 401. An operating circuit is thereby completed for relay SS on FIG. 5. This circuit extends from negative potential through make contact SN2-3, the Winding of relay SS and diode SD2, over lead 50S, through diode 4D2,

over lead 401 and through operated key SSKl to ground potential. Relay SS is locked operated through its own make contact SSI-1.

Capacitor SCI is normally charged over a circuit extending from ground potential through resistor SRS, capacitor SCI, resistor SR4 and resistor SRS to negative potential. When ground potential is applied to lead 401 through operated key SSKI, capacitor SCII starts to discharge over a circuit extending from capacitor SCI through resistor SR4, over lead S05 and through diode 4D2 to the ground potential on lead 401. As capacitor SCI is thus being discharged, current is drawn from negative potential through make contact SNI-1, resistor SR1 and Zener diode SDI. When the voltage drop across resistor SR1 becomes sufliciently large, the Voltage applied to Zener diode SDI becomes less than the voltage threshold of Zener diode SDI. At this time the base of transistor ST 2 is eiectively at ground potential, and transistor ST2 is turned OFF. Zener diode SDI reduces the time required to turn transistor ST2 OFF by blocking the application of negative potential to the base of transistor ST2. l When transistor ST2 is turned OFF, the operating circuit for relay SN2 is opened and rel-ay SN2 releases. The release of relay SN2 opens the operating and locking circuits for all PI relays at make contact SN2-4. Thus any -PI relays, such as 4PI, 7PI and SPI in the patient station control circuits of FIGS. 4, 7 and 8, which Were previously operated due to previous nurse-patient connections, Will be released When relay SN2 is released.

When capacitor SCI is suiiciently discharged and the voltage drop across resistor SR1 is thus lowered, the voltage' applied to Zener diode SDI Will again exceed its breakdown threshold. At this time, negative potential is again applied to the base of Itransistor ST2 and transistor ST2 is turned ON. The RC time constant of capacitor SCI and resistor SR@ determine the time interval during Which transistor ST2 is turned OFF.

The return of transistor ST2 to its ON condition causes relay SN2 to reoperate over its above-described operating circuit. Operation of relay SN2 completes an operating circuit for relay 4P1. This circuit extends from negative potential through make contact SN2-4, over lead S04, through the Winding of relay 4PI and diode 4DI, over lead 401 and through operated key SSKI to ground potential. Although this operating circuit Was previously completed by the momentary operation of relay SN2, it was opened when transistor ST2 was momentarily turned OFF before relay 4P1 could operate. Relay 4P1 is held operated over a circuit extending from negative potential through make contact SN2-4, over lead S04, and through the winding of relay 4131, make contact BPI-I and break contact 4P2-1 to ground potential. Since the operating -circuits for other -PI relays include other operated station selection keys SSK30, SSK60 and these keys SSKSO, SSK60 are not operated, only relay 4PI will operate When relay SN2 operates.

This momentary release 'of relay SN2 when a station selection key SSKI is operated permits the nurse sequentially to select patient stations PS1-P860 by momentarily operating various station selection keys SSKI- SSK60 Without replacing the nurse station handset NHSI 0r releasing the intercom pick-up key IPKI. Each time a station selection key SSKI-SSK60 is momentarily operated, the previously operated P1 relays of all patient station control circuits are released, and the -PI relay of the patient station circuit associated with the operated station selection key SSK1-SSK60 is then operated.

When relay 4131 operates, the tip and ring conductors 206 and 207 of the nurse intercommunication channel NIC are connected to the patient intercommunication channel PICI. The `connecting circuit extends from the nurse handset NHSI of FIG. 2 over conductors 222 and 223, through operated key IPKI, over conductors 206 and 207, through control unit SVSCU, over conductors SI2, S13, S14 and SIS, through make contacts EPI-6, 4PI-S, SP1-4 and 4P1-3, over conductors 312, 313, 314 and 31S, through the amplifier SAI at patient station PS1 and over conductors 316, 317, 31S and 319 to the microphone MI and speaker SI at the patient station PSI. When this intercommunication connection is established, the tone supplied by tone source STS is transmitted through control unit SVSCU and over the patient intercommunication channel PICI to lthe patient station PS1. This tone, which is broadcast over speaker SI at the patient station PSI, is heard by the patient and serves as a signal audibly indicating that the nurse -has connected to his intercommunications channel PICI.

The above-described operation of relay SS completed a circuit for operating relay SX. This circuit extends from negative potential through make contact SNl-I over lead S19 through the Winding of relay SX and through make contacts SN2-2 and SS4 to ground potential. Relay SX, in'operating, applies ground potential to the base of transistor ST1 through make contact SX-2 and resistor SR2. Capacitor SC2 is then discharged through resistor SR2 and make contact SX-2 to ground potential. The RC time constant of capacitor SC2 and resistor SR2 determine the time required for capacitor SC2 to discharge. This time is approximately one-half second. When capacitor SC2 is suiciently discharged, the potential applied to the base of transistor ST1 is lowered sutciently to remove the forward bias from the emitter-base junction and turn transistor ST1 OFF.

When transistor ST1 is turned OFF, approximately one-half second after the operation of relay SX, ground potential is removed from the winding of relay SWT and relay SWT releases. The release of relay SWT removes the output of tone source STS from the tip conductor 207 of the nurse intercommunication channel NIC, thereby removing the audible tone signal from nurse intercommunication channel NIC and patient intercommunication channel PIC1.

When relay 4P1 was operated, as described above, the locking circuit for relay 4NC was opened at break contact 4P1-1, and relay 4NC then released. The release of relay 4NC extinguishes the various audible and visual nurse-call signals which were provided, as previously described, to alert the nurse to a patient-to-nurse call. The operation of relay 4P1 initiates different visual signals which indicate the answering of the patient-to-nurse call and the busy state of the intercommunication channels NIC and PIC1 used for the patient-to-nurse call. Lead 503 is disconnected from lead 217 at make contact 4NC4, thereby removing the 60 i.p.m. alternating potential BB from lead 217 and silencing buzzer NBL Continuous alternating potential LB is applied through break contact 4E-2 and make contact 4P1-2 to leads 311 and 411 causing patient lamp PLI at patient station PS1 and station lamp SL1 at nurse station NS1 to light steadily. The 60 i.p.m. alternating potential LB previously applied over lead S06 is disconnected from leads 311 and 411 at break contact 4P1-2 upon the operation of relay 4P1. The condition of patient lamp PL1 and station lamp SLI is thus changed from a llashing to a steady light.

The emitter of transistor 4T2 is connected through varistor 4V1 to ground potential. Prior to operation of relay 4P1, the base of transistor 4T2 is also connected to ground potential through diode 4D4, break contact 4P1w1 and break contact 4P2-1. However, when relay 4P1 operates, ground potential is removed from base of transistor 4T1 at break contact 4P1-1. Negative potential applied to the base of transistor 4T2 through resistor 4R2 then forward biases the emitter-base junction of transistor 4T2, causing transistor 4T2 to turn ON. When transistor 4T2 is turned ON, continuous ground potential is applied to the base of transistor 4T4 over a circuit including varistor 4V1, transistor 4T2, resistor 4R4, break contact 4NC-1 and break contact 41E-6. Transistor 4T4 is thus turned ON continuously, and supplies continuous negative potential to lead 302 thereby causing door lamp DLI to be lighted continuously.

As previously described, the momentary operation of key SSKI at nurse station NSI applies ground potential to lead 401. The ground potential on lead 401 is applied through diode 4D1 and resistor 41-R3 to the base of transistor 4T1. The emitter of transistor 4T1 has negative potential applied thereto through make contact SN2-4 and over lead S04. The base-emitter junction of transistor 4T1 is thus forward biased and transistor 4T1 is turned ON.

When transistor 4'I`1 is turned ON, a circuit is completed `for the operation of relay 4F21. This circuit extends from negative potential through make contact SN2-4,

over lead S64, through transistor 4T1, the winding of l When relay y@P2 operates, transistor Lil-T1 is turned OFF by the shunting action of make contact 4P2-2. However, relay 4P2 remains operated over a locking circuit extending from negative potential on lead S04 through make contact 4P2-2, the winding of relay 4P2 and make contact 4P2-1 to :ground potential. v

The patient and the nurse can now communicate by way of the connected nurse intercommunication channel NIC and patient intercommunication channel PIC1. The patient communicates hands-free, i.e. without use of the patient station handset PHSI, by way of microphone M1 and speaker S1. The nurse communicates by way of the nurse station handset NI-ISI. If desired, the nurse station NSI may be equipped ywith a separate speakerphone arrangement permitting the nurse to communicate handsfree.

PRIVATE NUR S13-PATIENT I'NTERCOMMUNICATION When an intercommunication connection is established between nurse intercommunication channel NIC and patient intercommunication channel PIC1, as described above, the conversation between the nurse and the patient may be heard throughout the room in which patient station PS1 is located. The nurses voice is broadcast over speaker S1 and the patients voice is picked up through microphone M1. Since nurse-patient conversations may be highly personal to the patient or since other patients in the same room might be disturbed, provision is advantageously provided at patient station PS1 for initiating a transfer of the nurse-patient conversation from the patient intercommunication channel PIC1 to the patient telephone channel PTC1 associated with the patient station handset PHSl. When this transfer is accomplished, the nursepatient conversation is no longer broadcast from speaker S1 and may be privately carried on by way of the patient station handset PHSl.

When relay 4132 was operated, as previously described, the patient telephone channel PTC1 comprising leads 30'6l and 307 was connected through make contacts 4P2-S and 1PZ-4l to the nurse intercommunication channel NIC comprising leads 206 and 207. Since the switchhook SHI at patient station PS1 was not operated at this time handset PHSI was not connected to ring lead 307 and the connection of the patient telephone channel PTC1 to the nurse intercommunication channel NIC merely prepared the patient station control circuit of FIG. 4 for a possible subsequent transfer operation.

When the patient at patient station PS1 desires to communicate privately with the nurse at nurse station NSI, he merely picks up the patient station handset PHSI thereby operating switchhook SH1. The operation of switchhook SH1 removes ground potential from lead 308. As previously described, relay 4P1 is held operated over a locking circuit extending rfrom its winding through make contact 1PZ-6 to ground potential on lead 308. The removal of Iground potential from lead 308 causes relay 4P1 t0 release. When relay 4P1 releases, the connection of the nurse intercommunication channel NIC to the patient intercommunication channel PIC1 is opened at trnake contacts 4P1-6, 4P1-S, 4P1-44 and 4P1-3.

The operation of switchhook SHI completes the connection of the patient station handset PHSI to the patient telephone channel PTC1 comprisin-g tip and ring leads 306 and 307. Tip and ring conductors 306` and 307 of patient telephone channel PTC1 are normally connected through break contacts 4P2-S and y4132-4 to tip and ring conductors 304 and 30S and thence to telephone exchange 104, permitting patient station PS1 to originate and receive outside calls through handset PHSI. However, when relay 4P2 is operated, las previously described, the patient telephone channel PTC1 is disconnected from telephone exchange 104 at break contacts 4P2-S and 4P2-4. Therefore, when patient telephone channel PTC1 is connected to nurse intercommunication channel NIC, as described a'bove, the patient may converse privately with his nurse.

When relay 4PI releases, alternating potential LB is still applied to leads SII and 442 through make contact 4132-3 to maintain lamps LPI and SLI in a continuously lighted condition.

If the patient at patient station PS1 had fbeen using patient telephone channel PTCI for an outside call at the time the patient-to-nurse call was initiated and answered, ground potential would not have been applied through switchhook SHI to lead 308. Therefore relay 4132 would -not have fbeen operated and the preparatory connection between the patient telephone channel PTCI and the nurse intercommunication channel NIC would not have been made. The patient would then tbe able to converse with the nurse over patient intercommunication channel PICI and carry on his outside call conversation over patient telephone channel PTCI at the same time. In this circumstance, should the patient wish to converse privately with the nurse, he must first terminate his outside call. The patient may momentarily operate his switchhook SHI thereby ,applying yground potential to lead 3018. This momentary application of ground potential to lead 30S completes an operating circuit for relay 4P2, as previously described. :Relay 4P2 locks in an operated condition, as described above, connects patient telephone channel PTCI to nurse intercommunication channel NIC, as described above, and disconnectsl patient telephone channel PTCI from telephone exchange 104, as described above. When the patient again releases switchhookSHI at patient sta` tion PSI, lground potential is again removed from lead 3&8 and relay 4PI is released, as previously described. The release of relay PI disconnects nurse intercommunication channel NIC from patient intercommunication channel PICI, as described above. Thus, fby merely flashing the switchhook SHI at his station PSI a patient may disconnect from an outside call currently in progress over his telephone channel PTCI and transfer a patient-nurse conversation from his intercommunication channel PIC'I to his telephone channel PTCI.

Should a patient Wish to return the nurse-patient conversation to his intercommunication channel PICI he can replace his handset PI-ISI land thereby eiect a transfer of the nurse-patient conversation from his telephone channel PTCI to his intercommunication channel PICI. When the patient handset PHSI is replaced, ground potential is again applied to lead 30S. An operating circuit for relay 4P1 is thereby completed extending rom negative potential through make cont-act 5N2-4, over lead 50'4, through the Winding of relay 4PI and through make contact 4P2-6 -to ground potential on lead 308. The operation of relay 4PI connects patient intercommunication channel PICI to nurse intercommunication channel NIC through rnake contacts IPI-6, 4PI-S, 4PI-4 and 4PI-3, as previously described.

DISYCONNECTION The termination of a nurse-to-patient intercommunication connection is under the complete control of the nurse. Although the patient may control the .priva-cy of the nurse-patient conversation, he cannot elect a disconnection from the nurse station NSI. The nurse at nurse station NSI can terminate a nurse-patient call in any of three ways.

It the nurse replaces the nurse station handset NHSI, ground potential is removed from leads 224 and 203. The removal of ground potential from lead 203 opens the operating cir-cuit of relay SNI, as described above, and relay SNI is released. 'Ihe vrelease of relay SNI initiates the release of relay 5X by removing negative potential from lead 519 at make contact SNI-I. When relay SNI releases, relay 5N2 is released by the opening of make contact SNI-I. When relay 5N2 is released, negative potential is removed from the winding of relay 5S by opening make contact 5N2-3 and relay 5S is re- I6 leased. The release of relay SNZ removes negative potential from lead 504 by opening make contact 5N2-4. The remov-al of negative potential from lead 504 causes relays 4PI and 4P2 to release, thereby returning the patient station control circuit of FIG. 4 to its normal condition.

The release of relays 4PI and 4P2 extinguishes lamps LPI, SLI and DLI. Alternating potential LB is removed trom leads 31'1 and 411 -at make contact 4P1-2 or make contact 4P23 when both of these relays are released. Patient lamp PLI and station lamp SLI. are thus extinguished. The release of relay 4PI returns ground potential through break contacts `llPI-I -and 4P2-2 to the base of transistor 4T2. Transistor 4T2 is thereby turned OFF and ground potential is removed from the base of transistor 4T4. The removal of ground potential from the base of transistor 4T4 causes 'it to be turned OFF. Negative potential is thus removed from lead 302 causing relay DLCI to release and door lamp DLI to be extinguished. Thus the replacement of nurse handset NHSI eifects a disconnection of nurse intercommunication channel NIC from patient intercommunication channel PICI and the return of the patient station control circuit of FIG. 4 Iand the nur-se station control circuit of FIG. 5 to a normal condition.

The nurse may also terminate ya nurse-patient call by releasing intercom .pick-up IPKI. The release of key IPKI removes lground potential from lead 203 and initiates the sarne circuit operation described above for returning the control circuits of FIGS. 4 and 5 to a normal condition.

As previously described, the nurse may select another calling patient station, for example, patient station P830, without replacing her handset NHSI or releasing key IPKI. To sel-ect patient station PS3@ for finterconrrnunication therewith, the nurse momentarily operates key SSK30. Ground potential is then applied to conductor 701. This ground potential is extended through diode 7D2 to lead 505 on FIG. 7. As previously described, the momentary application of ,ground potential to lead 505 causes capacitor SCI to discharge, resulting -in the permanent release of all PI relays except that of the patient station cont-rol circuit associated with the selected patient station. rThus, the patient station control -circuit of FIG. 4 is returned to its normal condition responsive to the momentary operation of key SSK30, and the nurse is connected to patient intercommunication channel PIC30` in the same manner as previously described With reference to the connection of the nursepatient intercommunicat-ion channel PICI.

ANSWER FROM REMOTE STATION The occasion may arise when it is necessary that nurse station NSI be left unattended. Remote station RSI is provided to permit answering of patient-to-nurse calls at a location other than nurse station NSI. Remote station RSI maybe located in any convenient, nonmally attended area of the hopsital.

The remote station tran-ster key RTKI at nurse station NSI is manually operated by the nurse Whenever nurse station NSI is to be left unattended. Key RTKI, when operated, will lremain so until manually released. The operation of key RTKI connects ground potential over lead 225 to buzzer RBI at remote station RSI. Lead 217, over which alternating potential BB is supplied to activate buzzer NBI at nurse station NSI, is connected via lead 237 to buzzer RBI at remote station RSI. Thus, When key RTKI is operated, buzzer RBI is activated concurrently With buzzer NBI.

Tip lead 232 of nurse Itelephone channel NTCI is connected through operated Ikey RTKI to lead 220 and thence to the ringer (not shown) in remote station RSI. Ring lead 233 of nurse telephone channel NTCI is connected through operated key RTKI to lead 219 and thence to th@ finger in remote station RSI. Thus, incoming calls .1 7 over telephone channel NTCI which activate ringer NRI at nurse station NC1 also activates the ringer of nurse station RSI when key RTKI is operated.

As previously described, the operation by a patient of a nurse-call key NCK1-NCK60 initiates generation of a 60 i.p.m. audible nurse-call signal by buzzers NBI and RBI. In response to this audible signal, the attendant at remote station RSI may automatically answer a calling patient station PS1-P860 merely by lifting the handset RHSI of remote station RSI. When handset RHSI is lifted, ground potential is app-lied through the operated switchhook (not shown) of remote station RSI to lead 218, thereby operating relay SSC.

An operating circuit for relay SNI is completed through make contact SSC-1 when relay SSC operates. The operation of relay SNI turns transistor ST2 ON and completes an operating circuit for yrelay SN2 through transistor ST2, as previously described.

Assuming that patient station PS1 initiated the patientto-nurse call, relay 4NC lhas been operated already, as

` previously described. The operation of relay SN2 therefore completes an operating circuit for relay 4131.` This circuit extends from negative potential through make contact SN2-4, over lead S04, through the winding of relay 4P1 and diode 4D1, over lead 401 and lead 421, Ithrough make'contact 4NC-6, over lead S01 and through `break contact SX-I and make contact SSC-2 to ground potential.

Transfer contacts of all nurse-call relays, for example 4NC-6 and SNC-6, are arranged along lead 402 in a preference lockout type chain circuit. For example, if patient station P830 had initiated the patient-to-nurse call, relay 4NC would not be operated and relay 7NC would be operated instead. The ground potential applied to lead S01 Ithrough make contact SSC-2 would then extend over lead 402 through break contact 4NC-6 and make contact 7NC-6 to lead 701, thereby providing an operating circuit for relay 7PI. The preference chain circuit along leads 402 and 702 comprising transfer contacts 4NC-6-8NC-6 of the various nurse-call relays 4NC-SNC determines the order in which calling patient stations PSI-P360 are answered from remote station RSI. The order in which calls are answered may Ibe rearranged by manipulation of vthe preference circuit in accordance with the preference to be given the various patient stations PS1-P560.

The operation of relay 4PI initiates circuit operations in the patient station control circuit of FIG. 4 and the nurse station cont-rol circuit of FIG. identical to those previously described with reference to the answering by the nurse -of a patient-to-nurse call `at nurse station NSI. The handset RHSI of remotes-tation RSI is associated with tip and ring leads 226 and 227 of remote intercommanica-tion channel RIC. Leads 226 and 227 are connected to tip and ring leads 206 and 207 of nurse intercommunication channel NIC. As a result, the remote intercommunicati-on channel RIC is connected via tip and ring leads 206 and 207, control unit SVSCU, leads SI2, S13, S14 and S15, and make contacts iPI-, LiPI-S, 4P1-4 and 4P1-3 to the patient intercommunication channel PICI.

The operation of relay SWT, tone source STS, relay SS and relay SX is identical to that previously described. However, when relay SX is operated, the above-described opera-ting circuit for relay 4P1 is opened at make contact SX-I. The control of relay 4P1 is then transferred to the switchhook SHI at patient station PS1 to permit the patient to select either the intercommunication channel PICI or the telephone channel PTCI for conversing with the nurse at remote station RSI. The transfer operation between intercom-munication channel PICI and telephone channel PTCI is identical to that previously described.

When the nurse or attendant at remote station RSI wishes to terminate his conversation with the calling patient he replaces the handset RHSI. Ground potential is thereby removed from lead 218 and relay SSC is re- 18 leased. The release tof relay SSC causes the release of relay SNI `by opening make contact SSC-1. The remaining disconnect operations of the patient station control circuit of FIG. 4 and the nurse station control cir-cuit of FIG. 5 are identical to those previously described.

If more than yone patient station PS1-PS6() is calling the nurse, buzzer RBI will continue to provide a 60 i.p.m. audible signal. Sixty i.p.rn. alternating poten-tial BB is applied through a make contact, such as 7NC-4, of the -NC relay associated with the other calling patient stations, such as P830. The attendant at remote station RSI can sequentially answer patient-to-nurse calls by flashing the switchhook of remote station RSI to release an existing nurse-patient intercommunication connection and establish a connection to the next preferred patient station, such as P830, as determined by the above-described preference lockout chain circuit of -NC relay transfer contacts. When all patient-to-nurse calls have been answered and therefore a-ll -NC relays are released, the 6 0 i.p.m. audible signals from buzzer RBI will cease.

EMERGENCY .SIGNALING Each patient room, such as private -room of FIG. 3 or ward 102 of FIG. 6, is equipped with an emergency key EK1-EK30. These keys are of the locking type and must be manually released. They may be located in appropriate areas at which a patient might require immediate attention, such as the washroom. The operation of an emergency key, such as EKI, initiates various audible and visual signals differing from those initiated by a normal patent-to-nurse call. The emergency audible and visual signals take preference over the patient-tonurse-call signals and continue until the operated emergency key EK1-EK30 is manually released by the patient or the nurse.

For purposes of description it will be assumed that patient station P860 has initiated a normal patient-tonurse call, that patient station P830 is presently connected to nurse station NSI and that another patient in ward 102 now operates emergency key EK30.

Responsive -to the operation of key NCK60, relay SNC has been operate-d and the 60 i.p.m. control signals from interrupter S30 have been applied, as previously described, through make contact SNC-4 to lead 217, causing buzzer NBI at nurse station NSI to generate a 60 i.p.m. audible signal, and through make contact SNC-1 to the base of transistor ST4, causing door lamp DL30 to Hash at 60 i.p.m. Negative potential has been applied through make contact SNC-S to terminal 816.

Terminal 816 is cross connected over .a cross connec-V tion 710 to all corresponding terminals, such as 716, in patient station control circuits associated with other patient stations such as P830 in the same room 102. The negative potential applied to terminal 816 is extended over cross connection 710 to terminal 716, through diode 7DS, break contact 7NC-I and break contact 7E6 to the base Vof the transistor 7T4. In a similar manner negative potential is applied to the base elements of corresponding transistors in the patient station control circuits of other patient stations (not shown) located in the same room 102. Since the nurse is already in communication with another patient station P530 in the same room 102, transistor 7T 4 is continuously turned ON, as previously described, to cause door lamp DL30 to be continuously lighted. The above-described application of negative potential to the base of transisor '7T4 back biases the baseemitter junction thereof and turns transistor 7T4 OFF, thus removing the continuous negative potential from lead 602 and permitting the 60 i.m.p. negative potential supplied through transistor 8T4 to lead 602 to operate and release relay DLC30 at a 60 i.p.m. rate. Thus the 60 i.p.n1. flashing door lamp signal, indicating a patient-tonurse call, takes precedence over the continuous door lamp signal, indicating an existing connection between a patient and a nurse.

When key EK30 in Ward 102 is oper-ated, ground potential is applied to lead 601. An operating circuit for relay 7E, extending from negative potential through the winding of relay 7E, over lead 601 and through operated key EK30 to ground potential is thereby completed.

The operation of relay 7E applies continuous alternating potential BB through make contact 7E4 to lead 217. Regardless of what other signals are applied to lead 217, the application of continuous alternating potential BB thereto causes buzzer NBI to generate a continuous audiblesignal indicating an emergency call.

The operation of relay 7E connects the 120 i.p..m. alternating potential LB present on lead 509 through make contact 7E-3 to conductor 711, which, in turn, is connected to conductor 611. The continuousalternating potential LB already present on leads 611 and 711 as a result of the intercommunication call in progress between patient station PS30 and nurse station NSI is disconnected at break contact 713-2 when relay 7E operates. Patient lamp PL30 and station lamp SL30 therefore are flashed at 120 i.p.m. t-o visually indicate an emergency call.

The operation of relay 7E causes negative potential to be applied to the base elements of all other T4 transistors of patient station control circuits such as FIG. 8 associated with patient stations such as PS60 in the same room 102. For example, negative potential is applied through make contact 715-5y to terminal 715, over cross connection 709` to terminal 815, and through diode SDS and break contact 8E6 to the base of transistor ST4. Transistor ST4 is thereby back biased and maintained in its OFF condition permitting the emergency signals to take precedence over any other signals.

The operation of relay 7E connects the 120 i.p.m. ground potential on lead 507 through Iresistor '7R6 and make contact 7E-6 to the base of transistor 7T4. Any other potentials applied to the base of transistor 7T4 `are disconnected at break contact 71E-6 when relay 7E is operated. Transistor 7T4 is turned ON and OFP at a 120 i.p.m. rate in response to the 120 i.p.m. ground potential 'applied to its base. Negative Apotential is then applied through varistor 7V3 andtransistor 7T4, over lead 602 and through the winding of relay DLC30 to Iground potential. Relay DLC30 is thereby operated and released at a l2() i.p.m. vrate thereby causing door lamp DL30 to flash at a 120 i.p.m. rate. The rapid flashing 'of door lamp DL30 visually indicates an emergency call from the patients room or ward 102 associated therewith.

Thus the operation of an emergency key, such as EK30, initiates the hashing of' a station lamp SL30 at nurse station NSI, a lpatient lamp at patient station P830 and door lamp DL30 ata 120 i.p.m. rate, and initiates the generation of a continuous audible signal by buzzer N131 at nurse station NSI. -All emergency signals take precedence over Lany normal patient-tonurse signals or busy channel signals. Although the nurse can communicate with the patient station P830 from which an emergency signal is initiated by operating the .appropriate station selection key SSK30, the emergency signals cannot be released without the manual release of the emergency key EK30 in the patients room or Ward 102.

NURSE-TO.PATIENT CALL.

When a nurse at nurse station NSI Wishes to communicate with a patient, she momentarily operates the station selection key SSK1-SSK60 discretely associated with the patient station PS1-P560 with which she wishes t-o communicate. The resulting circuit operations are identical to those previously described with reference to the answering by the nurse of a patient-to-nurse call.

An audible signal supplied by tone source STS is transmitted to nurse handset NHS1 when handset NHSI is lifted and key IPKI is operated. A short burst of the same audible signal is transmitted to the selected patient over; hisy intercommunication channel, for example PICI, when. the. nurse momentarily operates the appropriate 20 station selection key SSKI. Lamps DLI, SLI, LPI and IL1 are continuously lig-hted until the nurse terminates the call, as previously described. The called patient may selectively transfer the ensuing nurse-patient conversation from his intercommunication channel PICl to his telephone channel PTCI, as previously described.

ROOM PRIVACY If the conversation in the patients room is private in nature, or if for some other reason the patient does not wish to be disturbed, he can, by operating his privacy key PK1, preclude the nurse from eavesdropping by way of microphone M1 and cause an audible signal to be returned to the nurse indicating his desire to be left undisturbed. However, the nurse at her dis-cretion can still talk to the patient through speaker S1 if it is felt necessary to disturb the patient.

The operation ofV privacy key PKI disconnects the microphone M1 from lead 316 of the microphone circuit, thereby precluding transmission of any conversation to the nurse over the intercommunication channel PICI. The operation of key PKI also connects lead 311 through `capacitors PCI and PC2 to lead 316. In the event of la nurse-to-patient call, continuous alternating potential LB is applied to lead 311, as previously described. When the continuous alternating potential LB on lead 311 is applied through operated key PKI to lead 316 of the microphone circuit, an audible signal is applied to the intercommunication `channel PICl. This audible signal is heard at nurse station N51 and indicates to the nurse that the called patient does not Wish to be disturbed.

Outside calls PATIENT CALLS Telephone exchange 104 may comprise any well-known manual or automatic switching center through which calls are completed to stations not within the intercommunication network, as previously described. Each patient station PSll-PS60 is equipped with aY telephone channel PTC1-PTC60 which is normally terminated in telephone exchange 104. For example, telephone channel PTC1 of patient station PS1 includes tip and ring leads 306 and 307 which are connected through break contacts 1PZ-5 and P2-4 to leads 304 and 305. Leads 304 and 305 are terminated in telephone exchange 104 and are also connected to the ringer PRI of patient station PS1. Ringing signals from telephone exchange 104 whichv are transmitted over conductors 304 and 305 initiate the generation of an audible signal by ringer PRI regard-less of the operative vcondition of relay 4132. Thus, Whether or not the patient telephone channel PTCI is in `use for nurse-patient intercommunication, an incoming call signal from telephone exchange 104 will produce an audible signal from ringer PR1. As previously. described, relay SP2 is not operated unless a nurse-to-patient connection has been established. Therefore, break contacts 4P2-5 and 4P2-4 are normally closed and the patient as patient station PSI can originate and receive outside calls using the handset PHS1.

An occasion may arise when a patient cannot be reached due to his absence from the room. -If telephone exchange 104 is ofthe manual type, the opera-tor may light; a message-waiting lamp, such as MWLI at patient station PS1, to indicate that she has a message for him.y For example, potential maybe applied to lead 303 at telephone exchange 104 causing lamp MWLI at patient station PS1 to be lighted.

As previously described, should a patient already be engaged in an outside .call over his telephone channel when the nurse initiates a nurse-to-patient call or when the patient initiates a patient-to-nurse call, both ycall conversations may be carried on at the same time. However, the patient must terminate his outside call before the nurse-patient conversation can be transferred to his telephone channel.

NURSE CALLS A nurse station, such as NSl, is equipped with one or more telephone channels, such as NTC1. Each telephone channel NTC1 is discretely associated with a line pickup key, such as LPK1. If it is desired to equip a nurse station NSI with more than one telephone channel, telephone exchange 104 may include additional key telephone equipment, as is well known in the art, to permit the various switching functions required for multiple line station pickup. The nurse can originate and receive outside calls through any of her telephone channels, such as NTC1, by operating the appropriate line pick-up key LPKl and lifting her handset NHS1. The nurse station NSI may be further equipped with a hold button (not shown) permitting the nurse to hold outside calls while she answers calls from herfpatients.

If desired, remote station RSI may be equipped with pick-up keys RLPKI, RIPKI similar to intercom pick-up key IPKl and :line pick-up key LPKl if desired. The tip and ring conductors, such as 228 and 229, of the nurse telephone channels, such'as NTC1, are then multipled at the appropriate pick-up keys RLPKl at remote station R81. It is to be understood that the above-described arrangements are illustrative of the application of the principlesof my invention. Numerous other arrangements may 4be devised by .those skilled in the art, without departing from the spirit and scope of my invention.

What is claimed is:

1. In a telephone system,

a pair of stations,

a pair of distinct and separate bidirectional voice intercommunication channels extending between said stations,

means for interconnecting said stations via one of said channels to permit voice communication lbetween said stations over said one channel,

and means at one of said stations for transferring said interconnection from said one channel to the other one of said channels to permit voice communication between said stations over said other channel.

2. In a telephone system,

the combination according to claim 1 wherein the other one of said stations comprises a telephone handset and a switchhook, said transfer means being activated upon removal of said handset from said switchhook.

3. A telephone system comprising a first station,

a second station,

a telephone line discrete to said first station and extending from said first station,

switch means at said first station,

a telephone exchange for -connecting said first station via said discrete telephone line to other telephone lines under control of said first station,

an intercommunication voice channel discrete to said first station and separate from said telephone line for connecting said first station to said second station to permit voice communication between said first and second stations,

and transfer means remote from said first station and responsive to operation of said switch means when a conne-ction is established between said stations via said intercommunication channel for releasing said connection and for establishing a telephone connection between said stations via said telephone line to permit telephone communication between said first and second stations.

4. A telephone system in accordance with claim 3 wherein said transfer means comprises first control means discrete to said first station,

means controlled by said first control means for connecting said intercommunication channel to said second station when said first control means is operated,

second control means discrete to said first station,

means controlled by said second control means for con' necting said telephone line to said second stationand disconnecting said subscriber line from said telephone exchange when said second control means is 5 operated,

means controlled Aby said first control means and said switchymeans for operating said second control means when said first control means is'operated and said switch means is released,

and means controlled by said second control means and said switch means for releasing said first control means when said second control means, and said switch'means are operated.

5. A telephone system in accordance with claim 3 wherein said transfer means comprises first control means discrete to said first station,

means controlled by said first control means for connecting said intercommunication channel to said second station when said first control means is opersecond control means discrete to said first station,

means controlled by said second control means for 'connecting said telephone line to said second station and disconnecting said telephone line from said telephone exchange when said second -control means is operated;

and further comprising means at said second station operablefor selecting said first station,

means controlled by said switch means and responsive to operation of said station selection means for operating both said first and second control means when said switch means is releasedand for operating only said first control means when said switch means is oper-ated,

- means controlled by the operation of only said first control means and responsive to release of said switch means for operating said second Icontrol means,

and means controlled by the operation of said second control means and responsive to operation of said switch means for releasing said first control means.

6. A telephone system in accordance with claimv 3 wherein said transfer means comprises a first relay discretely associated with said first station;

make contacts controlled by said first relay for connecting said intercommunication channel to said second station;

a second relay discretely associated with said first station;

make contacts controlled by said second relay for connecting said telephone line to said second station;

break contacts controlled by said second relay for connecting said telephone line to said exchange network;

means for operating said first relay;

a first lockingvcircuit for said first relay including another make contact controlled by said first relay and another break contact controlled by said second relay;

an operating circuit for said second relay including a break -contact controlled by said switch means, said other make contact controlled by said first relay and said other break contact controlled by said second relay;

a second locking circuit for said first relay including another make contact controlled by said second relay and said break contact controlled by said switch means;

and a locking circuit for said second relay including make contacts controlled by said second relay.

7. A telephone system in accordance with claim 6 wherein said operating circuit further includes a transistor having emitter, Icollector and base electrodes,

said emitter being connected to negative potential,

said collector being connected through the winding of said second relay and said break contact controlled by said switch means to ground potential,

and said base being connected through said other make contact controlled by said first relay land said other break contact controlled by said second relay to ground potential.

8. A telephone system comprising a station, l

a master station,

a telephone line,

means at said station for completing the circuit of said telephone line,

a telephone exchange for connecting said station via said`telephone line to other telephone lines under control of said station,

an intercommunication channel,

first means for connecting said station to said master station via said channel to permit voice communication between said stations,

second means operable only when said -iirst means is operated and said circuit completing means is releasedv'for disconnecting said telephone line from said telephone exchange and for connecting said .telephone line to said master station,

and means responsive to operation of said circuit completing means only when said second means is operated for releasing said first means.

9. A telephone system .in accordance with claim 8 further comprising a microphone and a speaker at said station connected to. said intercommunication channel,

a conductor,

means for applying a signal 1to one end of said conductor when said station is connected via said intercommunication channel to said master station,

and means at said station operable -for disconnecting said microphone from said channel and connecting the opposite end of said conductor to said channel.

10.. A telephone system in accordance with Aclaim 8 wherein said intercommunication channel comprises a microphone circuit terminated in a microphone at said station and a speaker circuit terminated in a speaker at said station;

- and further'comprisin-g A a conductor -discretely associated with said station,

`means for applying a signal to one end of said conductor when said station is connected via said intercommunication channel to said master station,

.and means at said station operable for disconnecting said microphone `circuit from said microphone and connecting said microphone circuit to the lother end of said conductor.

11. A telephone system in accordance with claim 8 further comprising 1 a microphone at said station connected to said' intercommunication channel;

a speaker at sai-d station connected to said intercommunication channel;

a signal device at said station,

1 means for applyingenergizin-g potential to said signal device when said station is connected via said channel to said master stat-ion;

and means at said station operable for disconnecting said microphonefrom said channel and connecting said last named means to said channel.

12. A telephone system comprising a plurality of stations,

a master station,

meansat said master stat-ion for selectin-g each of said stations,

first means discrete to one of said stations responsive -toay irstoperation of said station selecting means for connecting said one station to said master'station,

second means discrete to another of said stations responsive to a second operation of said station selecting means distinct from said first operation thereof for connecting said other station to said master station, v

and control means responsive to said second operation n of said station selecting ymeans for releasing said first means immediately and for operating said second means after a predetermined time interval.

13. A telephone system in accordance with claim 12 wherein said cont-rol means comprises a velay;

-a transistor havin-g emitter, collector and -base electrodes;

an operating circuit for said relay serially including the emitter and {col-lector of said transistor;

an operating circuit `for said first means including a make contact controlled by said relay and a make contact controlled by said first operation of said station selection means;

an operating circuit for said second means including said make contact controlled by said relay and a make contact controlled by said second operation of said station selection means;

a locking circuit for said first means including said make contact controlled by said relay;

timing circuit means serially connected between the base of said transistor and sai-d station selection means;

and said timing circuit means responsive to operation of said station selection means immediately toturn said transistor OFF and, after a predetermined time interval, to turn said transistor ON.

14. A telephone system comprising a first station;

a master station;

a signal device associated with said first station;

a first station control circuit discretely associated with said Iirst station comprising a first transistor,

a first energizing circuit for said signal devi-ce serially including the emitter `and collector of said first transistor,

Vfirst switch control means -operable responsive to a call signal from said first station,

means controlled by said rst switch control means for applying forwa-rdabiasing potential to the base of said first transistor at a iirst rate of interruption causing said signal device to be energized at said first rate of interruption,

a second transistor,

second switch control means operable responsive to a station. selection signal from said master station,

means controlled by said second switch control means for connecting said first station to said master station when said second switch control means is operated, for applying forward-biasing potential to the base of said second transistor when said second switch control means is operated and for holding said first switch control means operated when said second switch control means is released,

means serially including the emitter and collector of said second transistor for applying continuous forwardbiasing potential to the base of said first transistor causing said signal device to be energized continuous- 1v,

third switch control means operable responsive to an emergen-cy signal from said first station,y

and means controlled by said third switch control means for disconnecting both said continuous forward-biasing potential and said interrupted forward-biasing potential from the base of said first transistor and for applying forward-biasing potential thereto at a second ratey of interruption causing said signal device to be energized at said second rate of interruption. 

1. IN A TELEPHONE SYSTEM, A PAIR OF STATIONS, A PAIR OF DISTINCT AND SEPARATE BIDIRECTIONAL VOICE INTERCOMMUNICATION CHANNELS EXTENDING BETWEEN SAID STATIONS, MEANS FOR INTERCONNECTING SAID STATIONS VIA ONE OF SAID CHANNELS TO PERMIT VOICE COMMUNICATION BETWEEN SAID STATIONS OVER SAID ONE CHANNEL, AND MEANS AT ONE OF SAID STATIONS FOR TRANSFERRING SAID INTERCONNECTION FROM SAID ONE CHANNEL TO THE OTHER 